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San Francisco Examiner

Look-Alike Study Shows Genetics Key To Personality Traits

August 26, 2014

Montreal— When twins have similar personalities, is it mainly because they share so much genetic material or because their physical resemblance makes other people treat them alike?

Most researchers believe the former, but the proposition has been hard to prove. So Nancy Segal, a psychologist who directs the Twin Studies Center at California State University Fullerton, decided to test it - and enlisted an unlikely ally.

He is François Brunelle, a photographer in Montreal who takes pictures of pairs of people who look alike but are not twins.

Segal was sent to Brunelle's website by a graduate student who knew of her research with twins. When she saw the photographs, Segal realized that the unrelated look-alikes would be ideal study subjects: She could compare their similarities and differences to those of twins.

"I reasoned that if personality resides in the face," she said, "then unrelated look-alikes should be as similar in behavior as identical twins reared apart. Alternatively, if personality traits are influenced by genetic factors, then unrelated look-alikes should show negligible personality similarity."